1. Field of the Invention
The invention relates to a ski binding for a cross-country or touring ski.
2. Description of the Related Art
The type of ski binding mentioned in the introduction is described in Austrian Patent B 357,081. This binding is put on by inserting the sole extension of the ski boot into a retaining shell, during which procedure converging side walls of the stirrup facilitate the insertion. When the retaining shell is then pressed down, which causes the binding to be locked, locking pins enter retaining shell and openings in the sole extension of the ski boot. One disadvantage of this binding is that the retaining shell with its sole plate tilts about an axis located rather far behind and that the swivel axis for the relative motion of the retaining shell and the pivoting part carrying the locking pins lies substantially above the ski surface, thus preventing a natural rolling movement of the sole of the foot on the upper side of the ski. The insertion of the ski boot into the retaining shell from the bottom upwards is unnatural and thus uncomfortable. Furthermore, the anchoring of the retaining shell on the lateral surfaces of the ski is disadvantageous for reasons of stability. Also, arrangement of a movable element projecting outwards from the lateral surfaces of the ski deleteriously affects the skier's motions.
The invention has for its object to adapt, in a ski binding of the kind referred to in the introduction, the skier's stepping into the binding with the ski boot and his striding to the natural motions of the foot and to provide a compact arrangement of the entire ski binding.
This object is achieved by the features of the present invention.
The expedients advocated by the invention ensure an easy and safe stepping into the binding and natural motions during the striding. The whole binding has a compact construction so that there are no components that would protrude from the sides of the ski.
With the ski binding which is described in an older non-prepublished European Application (No. 85112147.5) of the applicant and which constitutes an internal state of the art, retaining shell and pivoting part can be pivoted about a common transverse pin against an elastic element. This transverse pin is held by a supporting structure mounted on the ski. The transverse pin is located in the front area of the two aforementioned components and a spring exerts pressure on retaining shell and pivoting part with the object of forcing them apart. Furthermore, the spring plunger is mounted on an extension of the pivoting part on a pin and, when the binding is in the closed position, locks into a crossbar--provided with a latching groove--of the retaining shell.
Generally, this construction has stood the test of time, but the retention of the ski boot was unsatisfactory, because it wobbled in the retaining shell. In addition, the presence of snow in the binding made stepping-in difficult. Also, there was no expedient that would prevent the spring plunger from opening inadvertently when it strikes an obstacle during striding. The spring that serves to force apart retaining shell and pivoting part is limited in its dimensions, and thus also in its action, because of design considerations. On stepping into the binding, the retaining shell could swing downwards even before the ski boot was firmly seated in the retaining shell because of its limited closing force.
To overcome the disadvantages of this older approach, the invention aims at achieving several objects, which will be discussed hereinbelow. A first object is to improve the retention of the ski boot in the retaining shell, even in the event that there is snow in the binding.
This object is achieved by the present invention.
The expedients taught by the invention ensure good retention of the ski boot in the retaining shell.
By virtue of the expedients of the present invention the optimum angle of the bearing surfaces is fixed at about 45.degree. so that, on the one hand, if snow is deposited on the bearing surfaces the longitudinal displacement of the ski boot does not become excessive, which would be the case if the angles were smaller and would thus lead to a heavy load on the locking pin or on the hook-up element and, on the other hand, the bearing surfaces would still offer the ski boot sufficient lateral support, which would no longer be the case if the angles were greater. The binding will be less sensitive to limit testings because of these expedients.
A combination of the features of the present invention will result in a very advantageous construction of the front area of the ski boot.
The features of the present invention permit a snug fit of the hook-up element to the locking pin.
The present invention also produces other advantageous constructions of the hook-up element.
In addition, the features of the present invention define the supporting surfaces on the ski boot, with which the latter is propped up against the bearing surfaces of the retaining shell. These features also define the guide surfaces of the ski boot, such that the lower guide surface of the ski boot rests on the bottom of the retaining shell and the upper guide surface abuts from below on the guide ledges of the retaining shell.
The present invention also provides a plurality of openings in the retaining shell which ensure that snow in the binding will be expelled upon stepping into the binding. Combining the features of the invention result in guiding the snow in the binding to the openings in the retaining shell.
The present invention results in a design of the surface of the locking pin along which slides the hook-up element upon stepping into the binding until it reaches its final position. The spacings between supporting surfaces and hook-up element are chosen such that the hook-up element is under tensile stress after the ski boot has been inserted into the binding.
According to a second object of the invention, the spring plunger is to be provided with an additional catch without increasing the number of components.
According to the invention, the spring plunger has an additional catch, ruling out inadvertent unlocking during striding due to stresses and shocks.
The third object is to ensure that stepping into the binding always occurs under controlled conditions.
As a result of the expedients taught by the invention, the closing force of the retaining shell is increased upon stepping into the binding without additional parts and without reinforcing the springs that serve to ensure that stepping into the binding always occurs under controlled conditions.
The present invention ensures that the angle of traverse of the spring plunger during the closing of the binding is equal to the minimum angle of traverse during the opening thereof.
By virtue of the construction of the invention, the position of the spring plunger and of the retaining shell relative to each other in the open position of the binding is fixed.
In all the versions described above, the spring plunger, during the entire stepping-out procedure, must be held in the position in which he releases the pivoting part.
Accordingly, the invention has as fourth object the overcoming of this drawback as well and the provision of a ski binding in which the user has the possibility of supporting himself on the cross-country track with both ski poles during the stepping-out procedure.
A ski binding for cross-country skiing as taught by West German Patent A1 34 05 861 features a base plate which extends towards the tip of the ski in two cheeks, between which is a placed a grip lever which is under the influence of a torsion spring. The torsion spring presses the grip lever against a hold-down clamp for the ski boot sole and which can be pivoted about a further transverse pin placed between the cheeks and on which a step spur is also mounted. The step spur locks with its end from below into a recess of the sole of the ski boot.
In the stepping-in position of the binding, the hold-down clamp is held in place by the grip lever in that a guide curve of the grip lever laps over a cam of the hold-down clamp. When the sole of the ski boot approaches the base plate during the stepping-in procedure, the cam migrates along the guide curve and when the culmination point is exceeded, the hold-down clamp is swung into the locking position.
This binding has the drawback that the stepping motion of the skier is produced only by the elasticity of the sole of the ski boot but not by a joint plate in the binding. Therefore, this prior type of solution differs from the subject matter of the invention.
Obviously, various approaches are possible for the practical construction of the spring plunger, but the design defined in the invention has proved particularly suitable. With this design, only one additional torsion spring is needed to produce the desired effect.
In principle, it would be possible, in order to retain the leg of the torsion spring projecting into the groove of the spring plunger and which is relatively small in size, to provide a flat part in the bottom of the arcuate groove, on which the end of the spring is fixed by friction. However, this could occasionally lead to an unintentional swing of the spring plunger. This is prevented by the present invention.
The present invention overcomes the danger that the tip of the torsion spring leg does not get stuck in the spring plunger.
The present invention enables the spring plunger to return automatically to its indexed position as soon as the end of the leg has been pressed by the crossbar of the retaining shell over the latching projection of the groove.
The present invention increases the operational safety of the ski binding, since the necessary spring force is split into two halves of a stirrup, thereby considerably reducing the danger of buckling of the loaded leg of the torsion spring.
Further features, advantages and details of the invention will now be described in more detail in conjunction with the accompanying drawings in which two specific embodiments of retaining shell and ski boot, as well as two embodiments of the spring plunger, have been set forth for purposes of illustration.